Process of pickling metal articles.



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" is sulfite waste annrson r. HOIIFFMAN nun wrntmn M. tannin, or rrrrsnunen, rnmrs'znvnma.

. I rnocnss or mommaenant narrows.

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Ito Drawing; Application filcd To all whom it concern? Be it known that we, Abelson F. Herr IMAN and WILLIAM M. PARKIN, citizens of the United States, residing at Pittsburgh, in the county of Alle'ghen and State of Pennsylvania, have invente new and useful-Tmprovements in Processes of Pickling Metal Articles, of which the following is a specifi- The present invention relates to picklin metal articles, for example iron, steel an the like, either castings, wrought metal or any other variety of metal, and has particu lar reference to the preparation of iron and steel for coating with tin, zinc, enamel or the like. a

It has been the custom, for many years prior to our invention to pickle iron and.

steel in a bath of dilute sulfuric or h drochloric acids, or acid salts. In this pic ing operation, there is a considerable amount of bubbles of the bath, and this the workmen and metal stock with which) it may come into contact. .a heavy blanket of foam upon the' sur pickle liquor, the formation'of spray is avoided. A 7 material suitable-'- in many respects for the production of such a foam the so-called sulfite process. The'liqu'or as it comes from the digesten'after the eepe 'aration of the wood pulp, is found'to'contain, however, materials which. act "delete riously, by the production of a coating of the.

surface of the metal-"articles, which coating prevents the ready adhesion of tin or [zinc to the iron. We have found that this objection can-be overcomeby anytreatment'of is in the form of sulfite orbisulfitje.

In carrymg "out our process in the referred manner we' add to the wastev I to liquor, after separation 'fromthe n ne atortw t "rammed Apt. 3,

V e preferably It has been found that by the useof a material 5 capable -of producing ace of the, or mist dryness.

hquor, produced by boiling wood in a, solution of calcium bisulfite 1n the manufacture of wood pulp according to j'fisicz serial-m1 135,2 0.

-. ,amo 11nt of lime equivalent t h ty .Of

We then boil the mixture.

'lil16 liquor, and

Thi's' oauses' the precipitation .of'the free and combined sulfurous. apid, in the-form of neutral sulfites' which can be separated from the liquor by filtration, producing a by-product suitable for use in preparing new sulfite liquor. This treatment also removes, under. some conditions, a considerable amount of thcalcium'sulfate (this material ordinarily being present in small quantities'in-waste sulfite liquor, probably derived by oxidation). The-lime does not remove the sulfonic acid. compounds, lignone derivatives, gums, sugars and the like, which are the active materials in the production of the foam blanket.

While it appears that the materials actu ment above described for the removal ofsul- Y .fites has been found to remove the disadvan- .tage in question. lt appears as possible that presence of some other compounds which are [removed by the lime treatment.

f Theliquor, after treatment with lime, and

can be separated after boiling, from the insoluble ma ter for example by filtration. The liquor can then be 'concentrated if desired, either toa thick syrup like molasses, or to a pasty condition, or even to lln the ickletbath we preferably addan amount of the liquor, in any one of the three -three to ten lon of pickle has been m use for some time,-.1t is" able to add, from time to time,-further;$,mtll

this disadvantage may be due to-the' forms above mentioned, containing about f rain of solid matter er 'galliquor. After the pic eliquor quantities of the purified waste sulfite'liquor.

While the purified waste sulfite liquor con i tains calcium, this is in the form of complex organic bodies, which do not to any material extent, lead to the production of calcium sulfate, by adding said liquor to the pickle liquor, when the latter contains sulfuric acid. The presence of calcium sulfate in the pickle liquor, in any material amounts, we have {found to be objectionable, hence we prefer pgt to employ crude waste sulfite liquor.

While sulfite waste liquor from the treat- 7 I ment of various kinds of wood in the production-of pulp, has been found to be suitable for our process, We find that the waste liquor obtained by treating soft pine wood particularly, or soft woods of the pine found to produce a black scum or coating on the surface of the metal, of which. the exact chemical composition is not thoroughly understood, but which was found to interfere materially with tinning or galvanizing. After treatment of the waste liquor with lime, boiling and filtration, this liquor does not then produce such scum or coating.

We claim:

1. In the pickling of metals, the step of subjecting such articles to the action of a bath containing a scale-removing agent and a small quantity of neutralized sulfite waste liquor.

2. The process which comprises neutralizing sulfite waste liquor with basic calcium compounds, removing insoluble matters, and thereafter adding a relatively small quantity of the same to an acid pickle.

3. A pickle containing acid and sulfitefree waste sulfite liquor ingredients.

4. A process which comprises subjecting waste sulfite liquor to a treatment capable of freeing the same from materials which would upon treatment with acids, liberate sulfurous acid, and thereafter adding a relatively small amount of such treated Waste sulfite liquor to an acid pickling bath.

In testimony whereof we aflix our signatures.

ADDISON F. HOFFMAN. WILLIAM M. PARKIN. 

